What Is a Straightening Machine?
A Straightening machine is a set of rollers that stretch and compress the upper and lower surfaces of steel material to make it flat. In the process, elastic-plastic deformations are generated in the metal which reduce internal stresses and homogenize those that cannot be eliminated. The final result is a straight, flat, and defect-free product. Straightening machines are used in the manufacturing of solid bars, square and rectangular tubes and hollow profiles as well as wires.
The majority of straighteners on the market today fall into one of two categories. The first are known as’straighteners’ or ‘flatteners’ and are distinguished by relatively large diameter, widely spaced work rollers that are not backed up. The second category are known as ‘precision levellers’ and have far smaller work rollers that can be flexed. Precision levellers are able to correct more defects than straighteners such as camber, wavy edges and centre buckles as well as trapped stresses within the metal that cause it to stay bent after being rolled or annealed. They require greater power to operate than straighteners to achieve this because they work much harder on the material.
Stierli offers both types of straightening machines. They are based on the same principle of alternating compression and stretching of the work roll but have different designs to accommodate differing applications. In general, the larger the roller diameter and the narrower the centre distance spacing, the more power required to operate a straightening machine.
Another factor that determines the capacity of a straightening machine is its maximum straightening force. This is determined by the structure of a straightener and the bending moment that the work rollers can apply to the material. Excessive penetration of the rollers will result in poor straightening efficiency and can lead to slipped material across the machine or even broken work rollers.
Power requirements for a straightening machine are also highly dependent on the yield strength of the material being processed. Most straighteners are rated to a specific material and, when the rated material is changed, the power requirement will increase or decrease.
Finally, it is important to consider the method used for driving the work rolls. Some straighteners have separate drive motors for each work roll whereas others have an electronic load sharing system that distributes the load to both the top and bottom sets of drives. This is essential to ensure that the power required to straighten the material is evenly distributed throughout the entire system and does not exceed the capacity of any one drive. This will prevent overworking and damage to the machine.